microsoft/aspire · error · McpProtocolException

InternalError

InternalError

Error message

{errorMessage: 'Failed to fetch structured logs for trace: {ex.Message}' or dashboard API error message}

What it means

Thrown by ListTraceStructuredLogsTool.CallToolAsync when the HTTP call to the dashboard API for a trace's structured logs raises HttpRequestException. Message is either the dashboard API's own error text (direct connection) or 'Failed to fetch structured logs for trace: <ex.Message>'; code InternalError (-32603).

Solutions

  1. Confirm the dashboard API base URL is reachable and retry the trace query.
  2. Restart the AppHost (or re-fetch dashboard info) to refresh endpoints and token.
  3. Check proxies/firewalls/DNS for the dashboard host.
  4. Read the underlying HttpRequestException in the CLI logs ('Failed to fetch structured logs for trace from Dashboard API') for the socket-level cause.
Defensive patterns

Strategy: retry

Validate before calling

// Ensure dashboard API reachability before trace log queries
var response = await httpClient.GetAsync(apiBaseUrl, HttpCompletionOption.ResponseHeadersRead, ct);
response.EnsureSuccessStatusCode();

Try / catch

try
{
    await ListTraceStructuredLogsAsync(traceId);
}
catch (McpProtocolException ex) when (ex.Message.Contains("Failed to fetch structured logs for trace"))
{
    // Refresh dashboard endpoints/token and retry once
    await RefreshDashboardInfoAsync();
    await ListTraceStructuredLogsAsync(traceId);
}

Prevention

When it happens

Trigger: Requesting structured logs for a specific trace ID while the dashboard API endpoint is unreachable, the base URL/token is stale, or the proxied connection fails mid-request.

Common situations: AppHost/dashboard restarted so cached dashboard info is stale; telemetry endpoint temporarily unavailable; network proxy interference; trace requested concurrently with app shutdown.

Understand the failure class

Background: 'Something went wrong' / 'Request failed (500)' / 'HTTP error! status: 404' — what failed HTTP requests actually mean and how to find the real cause — this error's family across 28 libraries.

Related errors

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/258e494821a75c98. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Cli/Mcp/Tools/ListTraceStructuredLogsTool.cs:131

                {limitMessage}

                # STRUCTURED LOGS DATA

                {logsData}
                """;

            return new CallToolResult
            {
                Content = [new TextContentBlock { Text = text }]
            };
        }
        catch (HttpRequestException ex)
        {
            logger.LogError(ex, "Failed to fetch structured logs for trace from Dashboard API");
            var errorMessage = dashboardInfoProvider.IsDirectConnection
                ? await TelemetryCommandHelpers.GetDashboardApiErrorMessageAsync(ex, apiBaseUrl, httpClientFactory, logger, cancellationToken)
                : $"Failed to fetch structured logs for trace: {ex.Message}";
            throw new McpProtocolException(errorMessage, McpErrorCode.InternalError);
        }
    }
}

View on GitHub (pinned to 25830f84bd)